Control mechanism for liquid coating apparatus



Nov. 2, 1943. c. L. MARTIN 2,333,543

CONTROL MECHANISM FOR LIQUID COATING APPARATUS Filed June 12, 1941 Patented Nov. 2, 1943 v um'rao STATES {PATENT OFFICE CONTROL MECHANISM FOR LIQUID COATING APPARATUS Clair L. Martin, Indianapolis, Incl, assignor to The American Paper Bottle Company, Toledo, Ohio, a corporation of Ohio Application June 12, 1941, Serial No. 397,796

4 Claims.

This invention relates to coating apparatus and more particularly to coating apparatus of the type designed and intended to be used in the application to the surface of an article of a coating of a substance in liquid form which substance, however, is solid at room temperatures and hence can only be applied as a liquid coating when in molten condition.

Various mechanisms for applying to the surfaces of articles such as paper containers molten coating substances such as paraffin have heretofore been successfully employed, and one such apparatus is fully disclosed in Patent 2,133,214, granted October 11, 1938 to Henry T. Scott.

That apparatus includes a container for a bathv of molten coating material and a conveying mechanism for lowering containers into the bath, moving them through the molten coating material and thereafter withdrawing them. Each container as it emerges from the bath carries with it an appreciable amount of coating substance, and hence it is necessary to replenish the bath from time to time. In the case of an apparatus which is operated at relatively slow speed, it is easily possible to provide simple means for automatically maintaining the level of the molten coating substance in the bath between predetermined limits. however, and particularly when containers of relatively large size, as compared with the cubic contents of the bath, are being coated it is much more difficult to maintain the level of the molten coating substance at the desired elevation. Due to the fact that the cubic volume of the bath itself is not'very great in a machine of thistype, the volume of coating liquid may be depleted in a relatively short time during the operation of the apparatus to such a point that satisfactory coating is not possible in the event that fresh coating liquid is not supplied in the proper quan-. tities at the proper time. It is, of course, neces- .course, necessarily meansthat, unless the action of the heating means is carefully controlled, an excessive amount of coating substance maybe melted and caused toflow into the bath, to inter-; fere with the coating operation.

At higher speeds of operation,

It is an object of the present invention to provide a coating apparatus for coatingarticles with a substance such as paraffin, solid at room temperatures and liquid at elevated temperatures. having associated therewith a liquid replenishing means which will satisfactorily maintain the level of the liquid within the bath within closely spaced predetermined limits despite the fact that the bath is of relatively small capacity and coating liquid is withdrawn therefrom at a relatively rapid or at a variable rate. The liquid supply means contemplated hereby is particularly suitable for use in association with a coating apparatus which comprises only a portion of an automatically operating apparatus which contains other cooperating mechanism. Where the coating apparatus is primarily intended for the coating of paper containers, for instance when it comprises one element of a complete automatic container forming, coating, filling and sealing machine, the operation of the machine may be interruptedat any time for any one of a number of reasons, and it is, of course, essential that the in-fiow of coating material into the bath be promptly diminished when there is any such interruption in the withdrawal of such liquids, to prevent flooding.

The mechanism which comprises the subject matter of the present invention, while of general utility, has been designed particularly to eliminate the possibility of failure of supply or of over-supply of coating liquid to an apparatus of the type disclosed in the Scott patent previously referred to and has been found to possess great utility. One form of the invention is illustrated by way of example in the accompanying drawing ducing articles intoand withdrawing them from the bath is generally indicated at H], the level of the upper surface of the bath at I I, and the con,- veyer mechanism for handling the.containersl'at E2. The details. of the casing l0 and conveyer l2 may be varied widely and will not bedescribed inasmuch as they do not comprise portions of the presentzinvention, It may be said however that the casing Ill includesa laterally ofiset, portion llia located at about the level of the surface of the bath, and in this offset portion, which is at all times in full communication with the interior of the casing, is positioned a fioat l3 from which projects upwardly a stem l4 slidably fitting within a guide tube I5, the stern l4 having secured to its upper end the disc l6. Disk l6 will of course rise and fall with the rising and falling movements of the fioat i3 and thereby indicate, exteriorly of the casing, the position of the upper surface of the bath.

Supported in position above the level of the bath and preferably attached to the outer casing I is a chamber I8 adapted to receive blocks of coating material in solid form, several of these blocks being indicated at 19. The blocks may be horizontally or vertically disposed as desired and as one is melted another may be added to maintain a substantial supply of solid coating material in the chamber l8 at all times. Molten material following onto the floor of the chamber II will pass downwardly through the chute or drain 2!! through the wall of the chamber l0 and drop into the bath.

The heating means associated with chamber l8, and whereby the paraffin or other blocks l9 may be heated to melting temperature preferably comprises a steam duct 22 having an inlet 23 and an outlet 24, the substantially horizontal portion 22 being preferably seprentine or in the form of a horizontally extending chamber of an area approximately equal to the area of the bottom of the paraffin block i9 which rests upon it. Live steam passing through the passage 22 will raise the temperature within the heating chamber l8 to such an extent thatall of the exposed surfaces of the parafiin blocks will be raised to melting temperature, but naturally the most rapid melting will occur at that surface of the undermost block which engages the heating member 22. Flow of steam through inlet duct 23 is controlled by a solenoid operated steam valve, all parts of which are housed within the casing or housing 26 and the solenoid is normally energized when the coating apparatus is in operation to permit the passage of steam for heating purposes. I

The conveyor mechanism i2 is electrically actuated as by means of a motor, .diagrammatically indicated at 30 in Figure 2. Current is supplied to motor 30 through mains 3| and a switch for controlling the flow of current through these mains to the motor, together with electromagnetic means for actuating the same, is diagrammatically indicated at 32. A normally open control switch is indicated at 33, and a normally closed control switch at 34, these switches being relatively closely spaced and each having a switch blade operating arm which lies in the path of movement of the disc I 6, previously referred to. As the level II of the surface of the bath rises, the disc IE will approach and finally contact with and operate the switch operating arm 34a of the normally closed switch 34 and will eventually cause this switch 34 to open. When disc l descends, it will approach and finally contact with and actuate the switch operating arm 33a of the normally open switch 33, thus closing this switch.

When the normally closed switch 34 is opened by the disc l6 because of the rising of the float H, the circuit through the electromagnetic means controlling the steam valve -is interrupted, and

duct I 8. When the switch blade 33a is actuated due to falling of the level of the bath, and the switch 33 is closed, a signal light, such as indicated at 35 will be energized, or some other signaling device such as a bell may be operated, and likewise the electromagnetic means 32 will be energized to open the switch controlling the fiow of electric current through main 3|, the motor- 30 thus being 'de-energized and the motion 01' the conveyer i2 halted. Hence, should for any reason the level of the liquid in the bath fall to an unduly low level the operator of the machine would be notified by signal and likewise the operation of the machine will be halted. It may not be again started until an adequate amount of coating material is added to the bath.

Should the level of the surface of the bath rise to a dangerous height, as may tend to occur when the mechanism is temporarily stopped so that no containers are passed through the bath to remove coating liquid, the steam fiow to the heating chamber is promptly interrupted and no further melting f the solid coating substance permitted. In case where the bath itself is of. small cubic content and' the rate of withdrawal of coating liquid is relatively rapid, the mechanism safeguards the apparatus in a most satisfactory manner, and has been found to be particularly suitable where containers of relatively large surface area, such for instance as paper containers of the two quart size, are being coated.

\ I claim: l

1. Apparatus for coating containers with a liquid coating substance such as parafi'm, in molten condition, said apparatus comprising a receptacle for a molten bath of such substance, a second receptacle for blocks of such coating substance in solid form and in which receptacle such blocks may be reduced to liquid form by the application of heat, a duct for leading molten material from said second receptacle to said first; receptacle, a fioat partially immersed in said bath and adapted to rise and fall with fluctuations in level of the surface thereof, a conduit for a heating fluid passing through said second receptacle, a valve for controlling the flow of heating fluid through said conduit, and electromagnetic means for normally holding said valve open, said means including a normally closed electrical switch, and means carried by the float for contacting with and opening said switch when the surface of the bath reaches a predetermined level.

2. Apparatus for coating containers with a liquid coating substance such as parafiin in molten condition, electrically energized mechanism including a control switch for placing articles to be coated in a bath of such substance and removing them therefrom, means for supplying molten coating substance, and electromagnetically actu-' ated means for controlling the fiowof such molten substance into the bath and for controlling the operation of said mechanism, said means including two spaced switches, one normally closed and the other normally open, and an element for closing the normally open switch when the liquid level falls and opening the normally closed switch when the liquid level rises.

3. The combination set forth in claim- 2 in which the normally open switch is in circuit with an electromagnet which when energized, will operate the control switch which comprises portion of said mechanism and controls the operation thereof.

4. Apparatus for coating containers with a liqassault electromagnetic means for controlling the opera-' tion of said control valve and of said mechanism,

said electromagnetic means including two spaced switches, one in circuit with said contro1.valve and normally closed and the other in circuit with said control switch and normally open, and an element for-closing the normally open switch when the liquid level tails and opening the nor-- mally closed switch when the liquid level rises. CLAIR L. MARTIN. 

